Power system including an electret for a power bus

ABSTRACT

A power system for an alternating current power bus includes an electret operatively associated with the alternating current power bus. The electret includes an output having an alternating current voltage when the alternating current power bus is energized. A rectifier includes an input electrically interconnected with the output of the electret and an output having a direct current voltage responsive to the alternating current voltage of the output of the electret. A powered device includes an input electrically interconnected with the output of the rectifier. The powered device is powered responsive to the direct current voltage of the output of the rectifier.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation of, and claims priority under 35U.S.C. §120 from, U.S. patent application Ser. No. 13/241,862, filedSep. 23, 2011, entitled “POWER SYSTEM INCLUDING AN ELECTRET FOR A POWERBUS”, the contents of which are incorporated herein by reference.

BACKGROUND

1. Field

The disclosed concept pertains generally to power bus apparatus and,more particularly, to power systems including an alternating currentpower bus. The disclosed concept also pertains to power systems for analternating current power bus.

2. Background Information

Inside of electrical control centers, as well as other electricalenvironments, there are bus bar wiring conductors and lugged cableconnection conductors, as well as conductor taps for three-phase power.This is true regardless whether the corresponding electrical product isfor low-voltage or for medium-voltage.

Electrical sensors of various types are used to detect the currentflowing through a conductor. Such sensors include, for example, a singleHall effect sensor that produces an output voltage indicative of thecurrent magnitude as well as more conventional current sensors such as ashunt resistor or a current transformer.

Hall effect devices have been used to sense variations in magnetic fluxresulting from a flow of current through a conductor. Some of theseknown devices have used a flux concentrator to concentrate magnetic fluxemanating from the flow of current through the conductor. It haspreviously been suggested that electrical current sensing apparatuscould be constructed in the manner disclosed in U.S. Pat. Nos.4,587,509; and 4,616,207.

It is also known to measure the current in a conductor with one or twoappropriately placed Hall sensors that measure flux density near theconductor and to convert the same to a signal proportional to current.See, for example, U.S. Pat. Nos. 6,130,599; 6,271,656; 6,642,704; and6,731,105.

U.S. Pat. No. 7,145,322 discloses a power bus current sensor, which ispowered by a self-powered inductive coupling circuit. A sensor sensescurrent of the power bus. A power supply employs voltage produced bymagnetically coupling the power bus to one or more coils, in order topower the sensor and other circuitry from flux arising from currentflowing in the power bus.

U.S. Patent Application Pub. No. 2007/0007968 discloses a system formonitoring an electrical power system including one or more transducerunits, each of which has a current measuring device and a voltagemeasuring device coupled to a respective one of the phase conductors ofthe power system, and a transducer wireless communications device. Thetransducer unit includes a battery for providing power to the componentsthereof. The battery is connected to a trickle charger, which, in turn,is electrically coupled to a phase conductor. The trickle charger is aknown parasitic power charger that draws power from the phase conductorand uses it to charge the battery.

A known prior proposal for monitoring a bus bar wiring conductor employsa current transformer to harvest energy or an associated signal, throughcoupling to the magnetic field caused by current flowing through theconductor. However, if a load is not connected to the conductor, and,thus, no current is flowing, then a current transformer (or magneticcoupling) will not function.

There is room for improvement in power systems.

SUMMARY

These needs and others are met by embodiments of the disclosed concept,which provide a power system for an alternating current power buscomprising an electret operatively associated with the alternatingcurrent power bus and a powered device powered directly or indirectlyfrom the output of the electret.

In accordance with one aspect of the disclosed concept, a power systemfor an alternating current power bus comprises: an electret operativelyassociated with the alternating current power bus, the electretcomprising an output having an alternating current voltage when thealternating current power bus is energized; a rectifier comprising aninput electrically interconnected with the output of the electret and anoutput having a direct current voltage responsive to the alternatingcurrent voltage of the output of the electret; and a powered devicecomprising an input electrically interconnected with the output of therectifier, the powered device being powered responsive to the directcurrent voltage of the output of the rectifier.

The powered device may be powered responsive to the direct currentvoltage of the output of the rectifier when the alternating currentpower bus is energized.

The alternating current power bus may have an alternating currentflowing therethrough.

Zero current may flow through the alternating current power bus.

As another aspect of the disclosed concept, a power system for analternating current power bus comprises: an electret operativelyassociated with the alternating current power bus, the electretcomprising an output having an alternating current voltage when thealternating current power bus is energized; and a powered devicecomprising an input electrically interconnected with the output of theelectret, the powered device being powered responsive to the alternatingcurrent voltage of the output of the electret.

As another aspect of the disclosed concept, a power system comprises: analternating current power bus; an electret operatively associated withthe alternating current power bus, the electret comprising an outputhaving an alternating current voltage when the alternating current powerbus is energized; and a powered device comprising an input powereddirectly or indirectly from the alternating current voltage of theoutput of the electret.

BRIEF DESCRIPTION OF THE DRAWINGS

A full understanding of the disclosed concept can be gained from thefollowing description of the preferred embodiments when read inconjunction with the accompanying drawings in which:

FIG. 1 is a block diagram of a power system including an electret, arectifier, and a powered device in accordance with embodiments of thedisclosed concept.

FIG. 2 is a block diagram of a power system including an electret and apowered device in accordance with another embodiment of the disclosedconcept.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

As employed herein, the term “number” shall mean one or an integergreater than one (i.e., a plurality).

As employed herein, the statement that two or more parts are “connected”or “coupled” together shall mean that the parts are joined togethereither directly or joined through one or more intermediate parts.Further, as employed herein, the statement that two or more parts are“attached” shall mean that the parts are joined together directly.

An “electret” is a dielectric material that has a permanent orquasi-permanent electric charge and/or dipole polarization, and also haspiezoelectric characteristics. The electret dielectric material istypically metalized for electrical connectivity and is fabricated insuch a fashion that an electric field exists within the dielectricmaterial. The electret is the electrostatic equivalent of a permanentmagnet. Electrets do not typically have the capability to generate muchcurrent but can be used to provide a reference potential difference.

As employed herein the term “switchgear device” shall expressly include,but not be limited by, a circuit interrupter, such as a circuit breaker(e.g., without limitation, low-voltage or medium-voltage orhigh-voltage); a motor controller/starter; a busway; and/or any suitabledevice which carries or transfers current from one place to another.

As employed herein the term “power bus” shall mean a power conductor; apower bus bar; a power line; a power phase conductor; a power cable;and/or a power bus structure for a power source, a circuit interrupteror other switchgear device, or a load powered from the power bus.

FIG. 1 shows a power system 2 for an alternating current (AC) power bus4. The power system 2 includes an electret 6 operatively associated withthe AC power bus 4. The electret 6 includes an output 8 having an ACvoltage 10 when the AC power bus 4 is energized. The power system 2 alsoincludes a rectifier, such as a suitable rectifier circuit 12, having aninput 14 electrically interconnected with the output 8 of the electret 6and an output 16 having a direct current (DC) voltage 18 (e.g., withoutlimitation, pulsed DC; full wave rectified DC; full wave rectified andfiltered DC) responsive to the AC voltage 10 of the output 8 of theelectret 6, and a powered device 20 including an input 22 electricallyinterconnected with the output 16 of the rectifier circuit 12. Thepowered device 20 is powered responsive to the DC voltage 18 of theoutput 16 of the rectifier circuit 12.

As shown in FIG. 1, the power bus 4 (e.g., without limitation, a powerbus bar or power conductor) is energized with an AC voltage 24 (withrespect to a ground or neutral potential (not shown)). The electret 6has two output terminals 26,28 for connection to the rectifier circuit12.

In this embodiment, the electret 6, having a permanent, inherentelectrostatic field (e.g., without limitation, when coupled to anadjacent energized AC power bus 4) provides a localized circuit groundpotential from which subsequent circuitry can be referenced. When an ACfield is present, the electret 6, which has a construction containing adielectric sandwiched by metal contacts, will behave like a capacitorand will charge in the presence of the AC field to provide stored energyto the output 8. For example, the electret 6 has a combination ofcharacteristics, such as permanent charge or dipole characteristics, andcan have internal electric field storage similar to a capacitor. Butsince it also has piezoelectric characteristics, it can act in concertwith a driving AC energizing voltage to be stressed through the internalelectric field (capacitive) effect and then “rebound” through thepiezoelectric effect to then generate the corresponding output ACvoltage 10. The output voltage and current is determined by the strengthof the AC field in the proximity of the electret 6, the duration thatthe electret 6 is present within the AC field, and the distance betweenthe electret 6 and the field generating power bus 4. This output voltageis converted from AC to DC through the use of the rectifier circuit 12.The output AC voltage 10 is converted to the output DC voltage 18 by therectifier circuit 12. The output DC voltage 18 of the rectifier circuit12 then can act on the powered device 20 (e.g., without limitation, ageneric device; a remote device) to be powered using current or chargestored internally through the internal electret electric field inconjunction with the internal piezoelectric character by the electret 6in the presence of the AC field. Use of the rectifier circuit 12 toconvert the output AC voltage 10 of the electret 6 to the output DCvoltage 18 of the rectifier circuit 12 is employed when the powereddevice 20 needs to be powered by DC voltage.

The electret 6, the rectifier circuit 12 and the powered device 20 areelectrically “floating” with respect to the power bus 4. None of this isdirectly electrically connected to ground potential or to the bus barpotential, such that the interaction is through the power bus ACelectric field. The electret 6 is adjacent to or suitably proximate thepower bus 4. The electret 6 is not actually electrically connected tothe power bus 4, although it may be suitably mechanically attached orcoupled thereto.

The electret 6 acts as a piezoelectric which also has a permanentcharge/dipole. The electret 6 interacts with the generated AC electricfield of the power bus 4. The electret output 8 provides anelectret-generated AC voltage 10.

EXAMPLE 1

The electret 6 may be an electret device. If a gap 30 is employedbetween the power bus 4 and the electret 6, then the gap distance is notcritically important. However, the closer the electret 6 is to the busbar 4, the more electric field can be harvested in order to provide morepower output. The overall electret device could be physically attachedto the power bus 4 (e.g., without limitation, employing adhesive, a boltor a clamp), in order to position it as close to the power bus 4 aspossible in order to harvest relatively more electric field. Theelectret 6 converts the AC electric field to the output AC voltage 10 ina robust yet passive manner.

EXAMPLE 2

The electret 6 may be made of an electret material solution packagedwithin, for example and without limitation, a molded housing (notshown).

EXAMPLE 3

The electret 6 may be made from a material selected from the groupconsisting of an organic polymer electret material, and an inorganicelectret material, although a wide range of electret materials can beemployed (e.g., without limitation, other organic materials; otherinorganic materials).

EXAMPLE 4

The electret 6 is coupled to the AC power bus 4.

EXAMPLE 5

The rectifier circuit 12 is selected from the group consisting of adiode, a full wave bridge, and an integrated device, although anysuitable rectifier circuit 12 can be employed, such as anotherequivalent circuit or discrete hardware. The rectifier circuit 12converts the AC output voltage 10 from the electret 6 into a DC outputvoltage 18 for the DC powered device 20 (e.g., a DC load).

EXAMPLE 6

The powered device 20 may be selected from the group consisting of awireless sensor, a remote sensor, a remote control device, a remotewireless sensor network, and a remote circuit.

EXAMPLE 7

The powered device 20 is powered responsive to the DC voltage 18 of theoutput 16 of the rectifier circuit 12 when the AC power bus 4 isenergized.

EXAMPLE 8

Further to Example 7, the AC power bus 4 has an alternating currentflowing therethrough.

EXAMPLE 9

Further to Example 7, zero current flows through the AC power bus 4.

EXAMPLE 10

The powered device 20 may have an equivalent circuit characteristicsimilar to that of a capacitor. In combination with the rectifiercircuit 12, the equivalent circuit characteristic, such as thecapacitor, can be charged through the use of the rectified DC voltage 18for use in powering the powered device 20.

EXAMPLE 11

Alternatives for the powered device 20 can include other suitableequivalent circuit characteristics. A possible constraint on the powereddevice 20 (e.g., without limitation, a wireless sensor; a remote sensor;a remote control; a remote wireless sensor network; remote sensingelements or remote circuits, associated with, for example and withoutlimitation, electrical control enclosures (e.g., without limitation,motor control centers (MCCs)) and associated bus bar and cable/wiringruns) is that it needs relatively low power or ultralow power, since theability for the electret 6 to provide substantial current may belimited. However, many such powered devices 20 are already designed toconsume relatively low power or ultralow power.

FIG. 2 shows a power system 32 for an AC power bus 34 including anelectret 36 operatively associated with the AC power bus 34. Theelectret 36 includes an output 38 having an AC voltage 40 when the ACpower bus 34 is energized, and a powered device 50 comprising an input52 electrically interconnected with the output 38 of the electret 36.The powered device 50 is powered responsive to the AC voltage 40 of theoutput 38 of the electret 36. The electret 36 and the power bus 34 maybe the same as or substantially similar to the respective electret 6 andpower bus 4 of FIG. 1.

In FIG. 2, the powered device 50 needs to be powered by an AC voltagesimilar to what comes directly out of the electret 36 when it isactuated by the AC power bus electric field. In this case, no rectifiercircuit is employed.

EXAMPLE 12

The power systems 2,32 of FIGS. 1 and 2 provide a power function for,for example and without limitation, electrical control enclosures (e.g.,without limitation, motor control centers (MCCs)) from a power bus 4,34that has been energized (e.g., by an applied AC voltage, even thoughelectrical current is not necessarily flowing or regardless whether aload is electrically connected).

EXAMPLE 13

The power systems 2,32 of FIGS. 1 and 2 make use of the AC electricfield that is generated in the space around a power bus 4,34 that isenergized. These employ the generated electric field to “turn-on” anelectret 6,36 that is susceptible to the electric field. The electret6,36 is held in a structure that allows for the electric field of theenergized power bus 4,34 to interact with the self-charged, self-fieldof the electret in a manner that actuates the electret.

EXAMPLE 14

The power systems 2,32 of FIGS. 1 and 2 harvest energy from an AC powerbus electric field through use of an electret 6,36. The charge of theelectret is acted on by the AC electric field to stress the electretmatrix, which in turn responds through its piezoelectric characteristicsto output a corresponding AC voltage 10,40.

EXAMPLE 15

The power systems 2,32 of FIGS. 1 and 2 generate useable energy from anenergized power bus 4,34 (e.g., by an applied voltage even thoughelectrical current is not necessarily flowing or regardless whether aload is electrically connected).

EXAMPLE 16

The power systems 2,32 of FIGS. 1 and 2 interact with an energized powerbus 4,34 through an electric field as opposed to a magnetic field thatis generated if current is flowing through the power bus. Hence, thissolves the problem of monitoring an energized power bus even if currentis not flowing (e.g., without limitation, a downstream circuit breakeris open; the downstream load is disconnected). This advantageouslyprovides a very beneficial result since an energized power bus couldhave a voltage (and an associated electric field) present without havingcurrent flowing and still be a danger to a person who accidentallytouched or approached the power bus.

EXAMPLE 17

For the power system 32 of FIG. 2, the input 52 of the powered device 50is powered directly from the AC voltage 40 of the output 38 of theelectret 36. For the power system 2 of FIG. 1, the input 22 of thepowered device 20 is powered indirectly through the rectifier circuit 12from the AC current voltage 10 of the output 8 of the electret 6.

EXAMPLE 18

The electrets 6,36 can be stand-alone devices in electricalcommunication with the rectifier circuit 12 and/or the powered devices20,50 (and any associated electronics (not shown)). Alternatively, theelectrets 6,36 can be part of a molded or a conventional housing (notshown) which contains some or all of the rectifier circuit 12 and/or thepowered devices 20,50 (and any associated electronics (not shown)).

While specific embodiments of the disclosed concept have been describedin detail, it will be appreciated by those skilled in the art thatvarious modifications and alternatives to those details could bedeveloped in light of the overall teachings of the disclosure.Accordingly, the particular arrangements disclosed are meant to beillustrative only and not limiting as to the scope of the disclosedconcept which is to be given the full breadth of the claims appended andany and all equivalents thereof.

What is claimed is:
 1. A power system for an alternating current powerbus, said power system comprising: an electret positioned adjacent tosaid alternating current power bus, said electret generating analternating current voltage when said alternating current power bus isenergized with a power bus alternating current voltage; and a powereddevice coupled to said electret for receiving said alternating currentvoltage, said powered device being powered responsive to the alternatingcurrent voltage, wherein the powered device is driven directly by saidalternating current voltage of the output of said electret and drivenindirectly but not directly by said power bus alternating currentvoltage.
 2. The power system of claim 1, wherein said electret comprisesa dielectric sandwiched between metal contacts.
 3. The power system ofclaim 1, wherein said electret is mechanically coupled to saidalternating current power bus.
 4. The power system of claim 1, whereinsaid powered device is selected from the group consisting of a wirelesssensor, a remote sensor, a remote control device, a remote wirelesssensor network, and a remote circuit.
 5. The power system of claim 1,wherein said powered device is powered by the alternating currentvoltage received from said electret when said alternating current powerbus is energized by the power bus alternating current voltage.
 6. Thepower system of claim 5, wherein said alternating current power bus hasan alternating current flowing therethrough when said alternatingcurrent power bus is energized by the power bus alternating currentvoltage.
 7. The power system of claim 5, wherein zero current flowsthrough said alternating current power bus when said alternating currentpower bus is energized by the power bus alternating current voltage. 8.A power system comprising: an alternating current power bus; an electretpositioned adjacent to said alternating current power bus, said electretgenerating an alternating current voltage when said alternating currentpower bus is energized with a power bus alternating current voltage; anda powered device coupled to said electret for receiving said alternatingcurrent voltage, said powered device being powered responsive to thealternating current voltage, wherein the powered device is drivendirectly by said alternating current voltage of the output of saidelectret and driven indirectly but not directly by said power busalternating current voltage.